Various drugs in dry powder form may be inhaled directly into the lungs through the mouth or nose. Inhalation allows the drug to bypass the digestive system and may eliminate the need for other more invasive drug application techniques, such as hypodermic injections. Direct inhalation can also allow smaller doses of a drug to be used to achieve the same desired results as the same drug taken orally. Inhalation can also help avoid certain undesirable side effects associated with taking a medicine orally or by injection.
One form of delivery device that is employed for inhaling a drug is the pressurized aerosol or metered dose inhaler (MDI). MDI's are, however, not suitable for use by all patients, e.g., small children, or for the administration of all medicaments. In addition, MDI's use propellants that can cause environmental damage. A widely used alternative is the so-called dry powder inhaler in which medicament powder is dispensed from an elongate gelatin capsule by causing the capsule to rotate and/or vibrate in an airstream, releasing the medicament that is inhaled by the patient. The capsules may be pierced by a suitable puncturing mechanism to release the medicament, or the capsules may be supplied in pre-pierced form. Additional packaging that prevents loss of powder from the capsule and the ingress of moisture is often necessary.
Gelatin capsules, and known drug delivery devices for inhalation, suffer from numerous disadvantages. For example, gelatin capsules are not impervious to moisture so exposure to the atmosphere can result in absorption of moisture. This may lead to agglomeration of the medicament powder particles. These problems may be particularly acute where, as is often the case, the medicament is hygroscopic. As a result, capsules must be packaged in secondary packaging such as a blister package, which significantly increases the overall bulk of the device. In addition, the secondary packaging can be unwieldy or difficult to open, particularly in an emergency situation where the medicine must be delivered as fast as possible under stressful circumstances.
Another disadvantage with the gelatin capsules is that they may become brittle. In this case, the piercing operation may produce shards or fragments that can be inhaled by the patient. In addition, gelatin is a material of biological origin and therefore often contains a certain amount of microbiological organisms, leading to possible contamination of the medicament.
Removal of the capsule from the secondary packaging and loading it into the device may require a degree of dexterity greater than that possessed by some patients. In addition, the motion of the elongate gelatin capsule within the device may be irregular, leading to incomplete or variable dispensing of the powdered medicament.
Other dry powder inhaler systems use foil based drug storage configurations. These systems also suffer from a variety of disadvantages. Many foil-based systems require complex manufacturing and filling processes. In addition, to open these foil based systems, external puncturing mechanisms, which can cause “dead spots” of trapped medication, are normally used.
Accordingly, an object of the invention to provide a capsule for delivery of powder or other medicaments while providing a barrier to moisture or other unwanted material that can degrade the medicament.
Another object of the invention is to provide a system for delivering a medicament in powder or liquid form that can use such a capsule without “dead spots” or complex manufacturing and filling requirements.
These and other objects and features of the invention will be apparent from the described description and the figures.